here's the background: had my system setup for about 5 years...i've changed out a couple items over time (game system, dvd player, dvr)...everything worked fine...we had to move everything to put down a new floor...so, i labeled everything and took it down...now that i'm putting it back together i've got a couple questions...

1) i have a digital audio cable running from my tv (mitsubishi 52" dlp - wd52525) to my receiver (yamaha), however i don't think this is necessary...in fact, i get no sound unless i run red/white audio cables from tv to receiver...so, i unplugged the digital audio and it appears to have had nothing to do with tv audio...do i need this cable? could it be used with my xbox or xbox 360 (haven't connected either of these yet to try them out)? like i said, i modified some pieces over time, so i'm wondering if this is one i needed previously but no longer need it...

2) prior to unhooking everything all worked well...no my center rear speaker has no sound...checked and checked again (5 times actually) the speaker wire connections...anything else i should check for sound? all other speakers work just fine...is there something else i should be checking, whether it be a receiver setting or another connection?

3) my yamaha receiver (htr-5740) lists the different settings on the front - CD, Tuner, Cable, etc...whichever is selected is underlined with a red line...now that i've hooked everything up again i've noticed something odd...if i select tuner, cd, or dvd (these are the 3 others i've tried) it is underlined with a bright red line, as expected...however, when i select cable to watch tv, it is a dull red line - used to be the same bright red line...any ideas on this? (i'm wondering/hoping that whatever is causing this is also causing the speaker to not work)...

hopefully someone has some tips to try...i am not an expert on these things...i hook it up once and hope i never have to change it later cause i know there'll be problems - just like i'm having...